The present disclosure relates to systems and methods for measuring the gas content in drilling fluids.
During the drilling of a hydrocarbon-producing well, a drilling fluid or “mud” is continuously circulated from the surface down to the bottom of the wellbore being drilled and back to the surface again. The drilling fluid serves several functions, one of them being to transport wellbore cuttings up to the surface where they are separated from the drilling fluid. Another function of the drilling fluid is to cool the drill bit and provide hydrostatic pressure on the walls of the drilled borehole to prevent wellbore collapse and the resulting influx of gas or liquid from the formations being drilled.
Analyzing the drilling fluid as it returns to the surface is recognized in the oil and gas industry as an important first appraisal of a potential hydrocarbon-bearing reservoir zone, thereby providing important data to guide subsequent evaluation and testing. Such analysis and testing is commonly referred to as “mud logging” analysis. Through mud logging, reservoir zones can be evaluated while they are being initially penetrated by measuring the formation gases present in the drilling fluid as it returns to the surface. The presence and concentration of hydrocarbon and non-hydrocarbon gases in drilling fluids relative to the depth can be used in designing stimulation operations and production operations, as well as in the assessment.
Mud logging analysis of drilling fluids is typically conducted off-line using laboratory analyses which require the extraction of a sample of the drilling fluid and a subsequent controlled testing procedure usually conducted at a separate location. Because the characteristics of the extracted sample of the drilling fluid often changes during the lag time between collection and analysis, off-line, retrospective analyses can be unsatisfactory for determining true characteristics of a drilling fluid.
Additionally, some mud logging analyses take hours to days to complete. Therefore, the drilling operation is often finished prior to completion of the analysis. As a result, proactive control of drilling operations cannot take place, at least without significant process disruption occurring while awaiting the results of the mud logging analyses.